⚡️ perf: add code minify js and css during the initial build proc…

…ess when the `pkg_env` enviroment variable is set to `prod` (#359)

build.rs

@@ -0,0 +1,80 @@
+//! A build module of the application which minifies the project's css and js files on build which
+//! helps reduce the initial page by loading the files faster.
+
+#![forbid(unsafe_code, clippy::panic)]
+#![deny(missing_docs, clippy::missing_docs_in_private_items, clippy::perf)]
+#![warn(clippy::cognitive_complexity, rust_2018_idioms)]
+
+// ------- Imports -------
+use lightningcss::stylesheet::{MinifyOptions, ParserOptions, PrinterOptions, StyleSheet};
+use minify_js::{minify, Session, TopLevelMode};
+use std::{
+    fs::{read_dir, read_to_string, File, OpenOptions},
+    io::{Read, Write},
+};
+
+// ------- Constants -------
+const COMMON_STATIC_SOURCE_CODE_FOLDER: &str = "./public/static/";
+const STYLE_FOLDERS: [&str; 2] = ["themes", "colorschemes"];
+const PACKAGE_ENVIRONMENT_VARIABLE: &str = "PKG_ENV";
+const PRODUCTION_PKG_ENV_VARIABLE_VALUE: &str = "prod";
+
+/// A main function which minifies both css and js files using `lightningcss` and `minify_js` when
+/// the `PKG_ENV` environment and it is set to the value of `prod`.
+///
+/// # Error
+///
+/// This function returns the unit type when the minification process runs successfully otherwise
+/// it returns a standard error.
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    if let Ok(pkg_env_var) = std::env::var(PACKAGE_ENVIRONMENT_VARIABLE) {
+        if pkg_env_var.to_lowercase() == PRODUCTION_PKG_ENV_VARIABLE_VALUE {
+            // A for loop that loops over each file name containing in the `colorschemes` and `themes` folders
+            // and minifies it using the `lightningcss` minifier.
+            for folder_name in STYLE_FOLDERS {
+                for file in read_dir(format!("{COMMON_STATIC_SOURCE_CODE_FOLDER}{folder_name}/"))? {
+                    let file_path = file?.path();
+                    let source = read_to_string(file_path.clone())?;
+
+                    let mut stylesheet = StyleSheet::parse(&source, ParserOptions::default())
+                        .map_err(|err| format!("{err}\n{:?}", file_path.file_name().unwrap()))?;
+
+                    stylesheet.minify(MinifyOptions::default())?;
+                    let minified_css = stylesheet.to_css(PrinterOptions::default())?;
+
+                    let mut old_css_file = OpenOptions::new()
+                        .write(true)
+                        .truncate(true)
+                        .open(file_path)?;
+                    old_css_file.write_all(minified_css.code.as_bytes())?;
+                    old_css_file.flush()?;
+                }
+            }
+
+            // A for loop that loops over each file name containing in the `public/static` folder and minifies
+            // it using the `minify-js` minifier.
+            for file in read_dir(COMMON_STATIC_SOURCE_CODE_FOLDER)? {
+                let file_path = file?.path();
+                if file_path.is_file() {
+                    let mut code = Vec::new();
+                    let mut js_file = File::open(file_path.clone())?;
+                    js_file.read_to_end(&mut code)?;
+
+                    drop(js_file);
+
+                    let mut out = Vec::new();
+                    minify(&Session::new(), TopLevelMode::Global, &code, &mut out)
+                        .map_err(|err| format!("{err}\n{:?}", file_path.file_name().unwrap()))?;
+
+                    let mut old_js_file = OpenOptions::new()
+                        .write(true)
+                        .truncate(true)
+                        .open(file_path)?;
+                    old_js_file.write_all(&out)?;
+                    old_js_file.flush()?;
+                }
+            }
+        }
+    }
+    Ok(())
+}